This invention relates generally to the field of gearing arrangements wherein the rotational speed of an output shaft is controlled and maintained at a substantially constant rate despite variation in the rotational speed of an input shaft. More particularly, the invention relates to such gearing arrangements comprising cluster gears.
Wind turbines, also known as wind machines, can generate power efficiently and at low cost, typically by driving an air compressor or electrical generator. The effective rotation rate of the wind machine is increased through the use of gearing assemblies, small drive wheels, pulley transfer boxes or the like. Wind machines that drive rotating input shafts connected to electrical generators, air compressors or the like at increased revolutions per minute (RPM) relative to the actual RPM of the wind machine are shown, for example, in U.S. Pat. No. 7,399,162 and U.S. Published Patent Application No. 2012/0121418, the disclosures of which are incorporated herein by reference. Ideally, the RPM of the wind machine is multiplied such that even relatively slow rotation of the blade apparatus of the wind machine in low wind conditions will be sufficient to provide the minimum desired RPM of the electrical generators, air compressors, etc.
In such systems it is desirable to maintain the rotation rate of the compressor or generator within its optimum RPM range. It is also desirable to maintain the RPM below a maximum value to prevent damage to the compressor or generator. This can be difficult in that the RPM of the wind driven power source varies as a result of wind speed. For example, a typical generator may work best at a rotational speed of 1800 RPM, or have a preferred range between 1750-1850 RPM, and have a maximum RPM somewhat higher. The rotational speed of the input or drive shaft from the wind machine may be much higher than the optimum speed, and thus may need to be reduced to produce the optimum RPM and to maintain the RPM below the maximum cutoff. The RPM from the wind machine will also not be constant as it will vary relative to changes in wind speed.
It is an object of this invention to provide a variable speed drive apparatus suitable for use with wind machines wherein the output rotational speed of the wind machine is monitored and mechanisms are provided to adjust the rotational speed as needed in response to an increase and fluctuations in the rotational speed of the input or drive shaft above the optimum RPM range.